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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 34 |
| 5 | 210 |
| 6 | 1574 |
| 7 | 13866 |
| 8 | 140340 |
| 9 | 1604284 |
| 10 | 20439484 |
| 11 | 287152488 |
| 12 | 4409695952 |
| 13 | 73482586464 |
| 14 | 1320533540808 |
| 15 | 25456195929232 |
| 16 | 523975944225280 |
| 17 | 11469534961767408 |
| 18 | 266038450202037728 |
| 19 | 6518167274358688512 |
| 20 | 168209881653024622944 |
| 21 | 4560447490191133853536 |
| 22 | 129593625015740116555072 |
[1,1,2,7,34,210,1574,13866,140340,1604284, 20439484,287152488,4409695952,73482586464, 1320533540808,25456195929232,523975944225280, 11469534961767408,266038450202037728, 6518167274358688512,168209881653024622944, 4560447490191133853536,129593625015740116555072] |